Allow rpc callers to pass ccache and service names
This allows code to use multiple ccaches without having to muck with the
process global environment variables (KRB5CCNAME).
https://fedorahosted.org/freeipa/ticket/6543
Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-By: Jan Cholasta <jcholast@redhat.com>